Re: [PATCH] tty: Add MOXA NPort Real TTY Driver

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Tue, Jul 14, 2020 at 06:24:42AM +0000, Johnson CH Chen (陳昭勳) wrote:
> This driver supports tty functions for all of MOXA's NPort series
> with v5.0. Using this driver, host part can use tty to connect NPort
> device server by ethernet.
> 
> The following Moxa products are supported:
> * CN2600 Series
> * CN2500 Series
> * NPort DE Series
> * NPort 5000A-M12 Series
> * NPort 5100 Series
> * NPort 5200 Series
> * NPort 5400 Series
> * NPort 5600 Desktop Series
> * NPort 5600 Rackmount Series
> * NPort Wireless Series
> * NPort IA5000 Series
> * NPort 6000 Series
> * NPort S8000 Series
> * NPort S8455I Series
> * NPort S9000 Series
> * NE-4100 Series
> * MiiNePort Series
> 
> Signed-off-by: Johnson Chen <johnsonch.chen@moxa.com>
> Signed-off-by: Jason Chen <jason.chen@moxa.com>
> Signed-off-by: Danny Lin <danny.lin@moxa.com>
> Signed-off-by: Victor Yu <victor.yu@moxa.com>
> ---
>  drivers/tty/Kconfig   |   11 +
>  drivers/tty/Makefile  |    1 +
>  drivers/tty/npreal2.c | 3042 +++++++++++++++++++++++++++++++++++++++++
>  drivers/tty/npreal2.h |  140 ++
>  4 files changed, 3194 insertions(+)
>  create mode 100644 drivers/tty/npreal2.c
>  create mode 100644 drivers/tty/npreal2.h
> 
> diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
> index 93fd984eb2f5..79b545269b71 100644
> --- a/drivers/tty/Kconfig
> +++ b/drivers/tty/Kconfig
> @@ -259,6 +259,17 @@ config MOXA_SMARTIO
>  	  This driver can also be built as a module. The module will be called
>  	  mxser. If you want to do that, say M here.
>  
> +config MOXA_NPORT_REAL_TTY
> +	tristate "Moxa NPort Real TTY support v5.0"
> +	help
> +	  Say Y here if you have a Moxa NPort serial device server.
> +
> +	  The purpose of this driver is to map NPort serial port to host tty
> +	  port. Using this driver, you can use NPort serial port as local tty port.
> +
> +	  This driver can also be built as a module. The module will be called
> +	  npreal2 by setting M.
> +
>  config SYNCLINK
>  	tristate "Microgate SyncLink card support"
>  	depends on SERIAL_NONSTANDARD && PCI && ISA_DMA_API
> diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile
> index 020b1cd9294f..6d07985d6962 100644
> --- a/drivers/tty/Makefile
> +++ b/drivers/tty/Makefile
> @@ -24,6 +24,7 @@ obj-$(CONFIG_CYCLADES)		+= cyclades.o
>  obj-$(CONFIG_ISI)		+= isicom.o
>  obj-$(CONFIG_MOXA_INTELLIO)	+= moxa.o
>  obj-$(CONFIG_MOXA_SMARTIO)	+= mxser.o
> +obj-$(CONFIG_MOXA_NPORT_REAL_TTY) += npreal2.o
>  obj-$(CONFIG_NOZOMI)		+= nozomi.o
>  obj-$(CONFIG_NULL_TTY)	        += ttynull.o
>  obj-$(CONFIG_ROCKETPORT)	+= rocket.o
> diff --git a/drivers/tty/npreal2.c b/drivers/tty/npreal2.c
> new file mode 100644
> index 000000000000..65c773420755
> --- /dev/null
> +++ b/drivers/tty/npreal2.c
> @@ -0,0 +1,3042 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * npreal2.c  -- MOXA NPort Server family Real TTY driver.
> + *
> + * Copyright (c) 1999-2020  Moxa Technologies (support@moxa.com)
> + *
> + * Supports the following Moxa Product:
> + * CN2600 Series
> + * CN2500 Series
> + * NPort DE Series
> + * NPort 5000A-M12 Series
> + * NPort 5100 Series
> + * NPort 5200 Series
> + * NPort 5400 Series
> + * NPort 5600 Desktop Series
> + * NPort 5600 Rackmount Series
> + * NPort Wireless Series
> + * NPort IA5000 Series
> + * NPort 6000 Series
> + * NPort S8000 Series
> + * NPort S8455I Series
> + * NPort S9000 Series
> + * NE-4100 Series
> + * MiiNePort Series
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/errno.h>
> +#include <linux/fcntl.h>
> +#include <linux/version.h>
> +#include <linux/init.h>
> +#include <linux/ioport.h>
> +#include <linux/interrupt.h>
> +#include <linux/major.h>
> +#include <linux/mm.h>
> +#include <linux/module.h>
> +#include <linux/ptrace.h>
> +#include <linux/poll.h>
> +#include <linux/proc_fs.h>
> +#include <linux/uaccess.h>
> +#include <linux/serial.h>
> +#include <linux/serial_reg.h>
> +#include <linux/slab.h>
> +#include <linux/string.h>
> +#include <linux/signal.h>
> +#include <linux/sched.h>
> +#include <linux/tty.h>
> +#include <linux/tty_flip.h>
> +#include <linux/timer.h>
> +#include "npreal2.h"
> +
> +static int ttymajor = NPREALMAJOR;
> +static int verbose = 1;
> +
> +MODULE_AUTHOR("<support@moxa.com>");
> +MODULE_DESCRIPTION("MOXA Async/NPort Server Family Real TTY Driver");
> +module_param(ttymajor, int, 0);
> +module_param(verbose, int, 0644);
> +MODULE_VERSION(NPREAL_VERSION);
> +MODULE_LICENSE("GPL");
> +
> +struct server_setting_struct {
> +	int32_t server_type;
> +	int32_t disable_fifo;
> +};
> +
> +struct npreal_struct {
> +	struct tty_port ttyPort;
> +	struct work_struct tqueue;
> +	struct work_struct process_flip_tqueue;
> +	struct ktermios normal_termios;
> +	struct ktermios callout_termios;
> +	/* kernel counters for the 4 input interrupts */
> +	struct async_icount icount;
> +	struct semaphore rx_semaphore;
> +	struct nd_struct *net_node;
> +	struct tty_struct *tty;
> +	struct pid *session;
> +	struct pid *pgrp;
> +	wait_queue_head_t open_wait;
> +	wait_queue_head_t close_wait;
> +	wait_queue_head_t delta_msr_wait;
> +	unsigned long baud_base;
> +	unsigned long event;
> +	unsigned short closing_wait;
> +	int port;
> +	int flags;
> +	int type;  /* UART type */
> +	int xmit_fifo_size;
> +	int custom_divisor;
> +	int x_char; /* xon/xoff character */
> +	int close_delay;
> +	int modem_control; /* Modem control register */
> +	int modem_status;  /* Line status */
> +	int count; /* # of fd on device */
> +	int xmit_head;
> +	int xmit_tail;
> +	int xmit_cnt;
> +	unsigned char *xmit_buf;
> +
> +	/*
> +	 * We use spin_lock_irqsave instead of semaphonre here.
> +	 * Reason: When we use pppd to dialout via Real TTY driver,
> +	 * some driver functions, such as npreal_write(), would be
> +	 * invoked under interrpute mode which causes warning in
> +	 * down/up tx_semaphore.
> +	 */
> +	spinlock_t tx_lock;
> +};
> +
> +struct nd_struct {
> +	struct semaphore cmd_semaphore;
> +	struct proc_dir_entry *node_entry;
> +	struct npreal_struct *tty_node;
> +	struct semaphore semaphore;
> +	wait_queue_head_t initialize_wait;
> +	wait_queue_head_t select_in_wait;
> +	wait_queue_head_t select_out_wait;
> +	wait_queue_head_t select_ex_wait;
> +	wait_queue_head_t cmd_rsp_wait;
> +	int32_t server_type;
> +	int do_session_recovery_len;
> +	int cmd_rsp_flag;
> +	int tx_ready;
> +	int rx_ready;
> +	int cmd_ready;
> +	int wait_oqueue_responsed;
> +	int oqueue;
> +	int rsp_length;
> +	unsigned long flag;
> +	unsigned char cmd_buffer[84];
> +	unsigned char rsp_buffer[84];

You seem to have two "static" buffers here, for your device, that you
semi-randomly write to all over the place, but I can't find any locking
or coordination between things that prevents multiple commands from not
just overwritting each other.

Also, how does the data get sent to the hardware at all?  I see
cmd_buffer[] being written to, but what reads from it and how does the
hardware get the data?

What am I missing here?

thanks,

greg k-h